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16 Cygni
| dec1 = | appmag_v1 = 5.96 | component2 = 16 Cygni B | ra2 = | dec2 = | appmag_v2 = 6.20 }} --> }} 16 Cygni or 16 Cyg is the Flamsteed designation of a triple star system approximately 69 light-years away from Earth in the constellation of Cygnus. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C. In 1996 an extrasolar planet was discovered in an eccentric orbit around 16 Cygni B. Distance The parallax of the two brightest stars were measured as part of the Hipparcos astrometry mission. This yielded a parallax of 47.44 milliarcseconds for 16 Cygni A and 47.14 milliarcseconds for 16 Cygni B. Since the two components are associated, it is reasonable to assume they lie at the same distance, so the different parallaxes are a result of experimental error (indeed, when the associated parallax errors are taken into account, the ranges of the parallaxes overlap). Using the parallax of the A component, the distance is 21.1 parsecs. The parallax of the B component corresponds to a distance of 21.2 parsecs. Stellar components 16 Cygni is a hierarchal triple system. Stars A and C form a close binary with a projected separation of 73 AU. The orbital elements of the A–C binary are currently unknown. At a distance of 860 AU from A is a third component designated 16 Cygni B. The orbit of B relative to the A–C pair was determined in 1999 and not updated since (as of June 2007): plausible orbits range in period from 18,200 to 1.3 million years, with a semimajor axis ranging from 877 to 15,180 AU. In addition B orbits between 100 and 160 degrees inclination, that is against the A–C pole such that 90 degrees would be ecliptical. Both 16 Cygni A and 16 Cygni B are yellow dwarf stars like the Sun. According to data from the Geneva–Copenhagen survey, both stars have masses similar to the Sun. Age estimates for the two stars vary slightly, but 16 Cygni is likely to be much older than the Solar System, at around 10,000 million years old. 16 Cygni C is much fainter than either of these stars, and may be a red dwarf. Measurements of the lithium abundance in 16 Cygni A and 16 Cygni B show a higher abundance in component A than is normal for a star of its age and mass, and higher than in 16 Cygni B. This enhancement may be due to a recent engulfment of a Jupiter-sized planet by 16 Cygni A, which increased the amount of lithium in the star's outer atmosphere. Planetary system In 1996 an extrasolar planet in an eccentric orbit was announced around the star 16 Cygni B. The planet's orbit takes 799.5 days to complete, with a semimajor axis of 1.69 AU. Like the majority of extrasolar planets detectable from Earth, 16 Cygni Bb was deduced from the radial velocity of its parent star. At the time that only gave a lower limit on the mass: in this case, about 1.68 times that of Jupiter. In 2012, two astronomers, E. Plavalova and N.A. Solovaya, showed that the stable orbit would demand about 2.38 Jupiter masses, such that its orbit was inclined at either 45° or 135°. The eccentric orbit and mass of 16 Cygni Bb makes it extremely unlikely that a terrestrial sized planet will be found orbiting within the star's habitable zone. For the 16 Cyg B system, only particles inside approximately 0.3 AU remained stable within a million years of formation, leaving open the possibility of short-period planets. For them, observation rules out any such planet of over a Neptune mass. There was a METI message sent to the 16 Cygni system. It was transmitted from Eurasia's largest radar—the 70-meter (230-foot) Eupatoria Planetary Radar. The message was named Cosmic Call 1; it was sent on May 24, 1999, and it will reach 16 Cygni in November 2069. http://www.cplire.ru/rus/ra&sr/VAK-2004.html The 16 Cygni system is within the field of view of the Kepler space telescope. See also * 61 Cygni * 30 Arietis * 83 Leonis * 54 Piscium * HD 20782 * HD 80606 * HD 89744 * HD 222582 References Vizier catalog entry for A Vizier catalog entry for B }} * External links * * * * * Category:Triple star systems BD+50 2847 and BD+50 2848 Category:Cygnus Cygni, 16 Category:G-type stars 0765.1 186408 and 186427 096895 and 096901 7503 and 7504 3